How Many Back Up Prepared For Asphaltene Onset Pressure Measurement Using Costly Collected Single Phase Bottomhole Fluid Samples?

Summary This study aims to improve asphaltene-risk evaluation using long-term data. Temporal changes in asphaltene risks with gas injection were evaluated. In reservoirs under gas injection, the in-situ fluid component gradually changes by multiple contact with the injected gas. Those compositional changes affect asphaltene stability, causing difficulty in risk prediction using asphaltene models. This study aims to reduce the risk uncertainty depending on operational-condition changes. Periodic upgrading of asphaltene models is essential for understanding the time-dependent changes of asphaltene risks. In a previous study, the asphaltene risk was evaluated for an offshore oil field in 2008 using the cubic-plus-association equation-of-state (EOS) models and using all the available data at the time. Additional experimental data were subsequently collected for a gas-injection plan. An additional study was performed that incorporated and compared the data sets. According to the previous study recommendation, additional asphaltene laboratory studies were conducted using the newly collected samples. All the asphaltene-onset pressures (AOPs) detected in the new samples were higher than those found in the previous study. A large difference was observed between the past and recent AOPs in the lower reservoir even though the samples were collected from the same well. The asphaltene-precipitation risk increases considerably because the new study detected AOP at the reservoir temperature, whereas no AOPs were detected in the previous study. The difference may be attributed to saturation-pressure increase. Next, the numerical asphaltene models were revised; the re-evaluated asphaltene-risk estimations were higher in the lower reservoir and slightly higher in the upper reservoir than the past ones. The reference sample fluids were collected from two different wells with different asphaltene and methane (C1) contents. The reliability of the new asphaltene laboratory results was increased by applying multiple data interpretation. Thus, the difference between the past and recent results can be attributed to fluid alteration with time. On the basis of the analysis in this study, the risk rating was updated to slightly higher than in the previous evaluation, emphasizing the importance of regular monitoring of asphaltene risks. This study provides valuable findings of time-lapse evaluation of asphaltene-precipitation risks for a reservoir under gas injection. The evaluations currently conducted in the industry are snapshots of instantaneous risks. Through the entire field life, the risks have varied depending on the operating conditions. This study demonstrates that risk estimates can change in a unique field with identical work flow by analyzing data collected at different times. Finally, this study demonstrates the importance of time-dependent reservoir-fluid properties.

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Study of the Long Term Acid Gas Sequestration Process in the Borzęcin Structure: Measurements Insight

Warnecki

Wojnicki

Kuśnierczyk

et al. 2021

Energies

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Geological sequestration of acid gases, including CO2, is now a growing solution to prevent progressive Earth climate change. Disposal of environmentally harmful greenhouse gases must be performed safely and securely to minimise leakage risk and possible uncontrolled emissions of injected gases outside the sequestration structure. The paper describes a series of research activities at the Borzęcin sequestration site located in western Poland, which were designed to study the migration paths of injected acid gases (mainly mixture of CO2 and H2S) into the water-bearing layers underlying natural gas reservoir. Along with understanding the nature and dynamics of acid gases migration within the sequestration structure, the research was also addressed to assess its leak-tightness and the long-term safety of the entire reinjection facility. As a part of the research works, two downhole sampling campaigns were completed in 2018–2019, where samples of water underlying the Borzęcin reservoir were taken and subsequently studied to determine their physicochemical parameters that were never before examined. Compositions of gas dissolved in downhole brine samples were compared with produced and injected gas. Relevant studies of reservoir water from selected wells were performed, including isotopic analyses. Finally, four series of soil gas analyses were performed on the area surrounding the selected well, which are important for the hazardous gas sequestration safety analysis in the Borzęcin facility. All the above mentioned research activities aimed to acquire additional knowledge, which is valuable for risk assessment of the acid gas sequestration process taking place on the specific example of the Borzęcin site operating continuously since 1996.

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How Many Back Up Prepared For Asphaltene Onset Pressure Measurement Using Costly Collected Single Phase Bottomhole Fluid Samples?

Cited by 4 publications

References 65 publications

Technical and Non-technical Challenges of Development of Offshore Petroleum Reservoirs: Characterization and Production

Technical and Non-technical Challenges of Development of Offshore Petroleum Reservoirs: Characterization and Production

Re-Evaluation of Asphaltene-Precipitation Risk Depending on Field-Operational-Condition Change/Variation: Case Study Comparing Risks in Past (2008) and Present (2016) for Future Prediction

Study of the Long Term Acid Gas Sequestration Process in the Borzęcin Structure: Measurements Insight

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